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Octane Mixing thoughts?

In a brief survey of web stuff I see a Mobil1 mfg's website that states(automotive myths) if mixing octanes into an empty tank they have different densities & so they say to be certain you do 1/2 into 1/2 to avoid them not mixing. I find that being double talk? It would seem to me that they either mix or they don't? What am I missing? www.Mobiloil.com -put "octane" in the search window, then see "automotive myths".
On a Wallace racing site www.wallaceracing.com they have a calculator allowing the formula to give desired final octane from whichever octanes based on total capacity. No further mention of what if stuff there.
It's also hard for me to imagine a bike tank not agitating the fuel enough to mix it , no matter the empty vs. 1/2 full idea.

I liked the sugar myth, it states "Back in 1994, researchers at Berkeley figured out sugar doesn’t dissolve in gasoline"

Heck they should have called me! I tried to do this over 45 years ago when I was about 10. I had an old REO motor off my grandfathers 50's lawn mower I use to play with, and I wanted to see what would happen, after hearing the sugar rumor. I dumped sugar in the tank and ran it till it ran dry, all it did was leave a pile of sugar in the bottom of the tank.

That motor was my mechanical "teething ring" Learned a lot taking it all apart and putting it back together, playing with the carb etc. Many a burn from the exhaust and ruined clothes from the oil. I pity the youth of today that just play on the computer all day.

As soon as you ride/drive off, the sloshing fuel is going to mix nicely. I have noted that Techron and other fuel system additive tell you to put that in the tank first, then fill it with gas. Can't imagine that is necessary either.

In a brief survey of web stuff I see a Mobil1 mfg's website that states(automotive myths) if mixing octanes into an empty tank they have different densities & so they say to be certain you do 1/2 into 1/2 to avoid them not mixing. I find that being double talk? It would seem to me that they either mix or they don't? What am I missing? www.Mobiloil.com -put "octane" in the search window, then see "automotive myths".

I once worked for a oil distributor. This included Mobil Oil franchises. You can't believe too much of what comes out of their mouths. In many cases, gas brands like Mobil, just distributes the gas. Refineries owned by different companies make the gas. All the gas comes from the refinery and goes into same distribution tank, and is distributed to different franchises (Gulf, Texaco, Mobil, etc). In our neck of the woods, Sunoco refined and distributed their own gas. We considered Sunoco superior to ours. I am sure there are others out west that may be like Sunoco.

In regards to this statement. The oil industry hates it when people mix gas octanes. They feel cheated out of profits. Even if there was some truth to Mobil's claim of different gas octanes settle out to different densities, the movement of the vehicle would mix it up. Today some oil distributors blend their own gas to different octanes, dyes, and mixtures (summer / winter blends).

In my opinion, mixing octanes should not be a problem. People have been doing it for decades.

Around here Sunoco used to have pumps offering four or five octane options. My understanding was that they had only two storage tanks, one a very low octane (about 2 points below "regular") and one high octane, and the pump mixed them in varying proportions. This may have changed. I stopped going to their stations because I felt I was getting suckered when their "regular" price was below all the other area stations - usually a comparable octane cost more than the station on the other corner.

Around here Sunoco used to have pumps offering four or five octane options. My understanding was that they had only two storage tanks, one a very low octane (about 2 points below "regular") and one high octane, and the pump mixed them in varying proportions. This may have changed. I stopped going to their stations because I felt I was getting suckered when their "regular" price was below all the other area stations - usually a comparable octane cost more than the station on the other corner.

Since they did everything themselves it was more expensive for them to refine the gas. They controlled 10% of the market while we control 90% of the market. Lower volume means a higher price to mfg. If you were just getting regular, then it probably isn't worth it. On the other hand, they didn't take any shortcuts in the refining and blending process. If I can buy Sunoco gas at the same price of other stations, I would buy from them in a heart-beat. If you want high-quality premium gas, they are the place to go.

A while back we had a thread about a 4 gallon minimum purchase. That included some discussion of blender pumps. 87, 89, 91 delivery from two tanks containing 87 and 91. Those pumps make 89 by blending the two.

Sure would hate to think that all the 89 I've bought from blender pumps in the past ten years had all the 91 settle to the bottom of by gas tank.

I call balderdash!

Paul Glaves - "Big Bend", Texas U.S.A
"The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russellhttp://www.bigbend.net/users/glaves

Mixing octanes happens all the time and you don't even know it. At a lot of retail gas stations when you get the mid-grade your actually getting a mixture of regular and premium. The station has two large tanks for the transports to drop premium and regular in. The dispenser actually mixed the right amount of regular and premium to give you the mid-grade octane rating. This does not happen at all locations or states but here in MI that is typical. Here you usually get a choice of 87, 89 and 93.

I used to sell bulk fuel and contracts for farmers and contractors. We also supplied many retail gas stations branded and unbranded. The main product all came out of same terminal (large storage tanks) and was additized depending on the branding (BP, Shell etc) based on what their criteria was. The additives were injected as the fuel went into the transport truck.

I've been logging this week & in going to my closest local station yesterday for 89, the Indians that bought it recently , evidently decided to drop the mid grade from the pumps. The pump price is blank on that of the 3 windows. I did .75g/87 & .75g/93 to get my1.5g of 2-cycle gas for mixing. I always shake my 2 cycle mix (meaning everytime,not justa @ oil addition)before I pour it in the machines as I read somewhere that it helps get a good mix after sitting.
i agree that the octanes don't seem to be a candidate for "layering". Good question for my Chem engr son!

Exactly what do you think is going on with these pumps that provide 3 or 4 choices of octane ratings by you selecting one by pushing a button. The system, pump, hose, etc still contain some of the previous sale before your choice reaches your tank, if you are worried about mixing octanes don't buy from this type outlet.

blending gasoline

Did that for a living. A typical blender may have 10 or more different componants being blended from butane to refformate. They mix, I sure wouldnt worry about mixing octanes. Oh yea, that is what we do. in the blender.